Tamper resistant lock

ABSTRACT

A tamper-proof key-operated lock is provided. The check point for the lock is displaced from the locked position, and the lock tumblers, while biased when the lock is in the locked position, are not biased at the check point. For preferred embodiments, a holding force is applied to the tumblers as they are moved from the locked position to the check point to prevent spurious movement of the tumblers. A one-piece, stationary biasing spring is also provided to reduce the cost of the lock.

[ June 19, 1973 United States Patent [1 1 Ignatjev TAMPER RESISTANT LOCK [76] Inventor: Vladimir lgnatjev, 39 Ledgewood Primary Examiner Robel-t Wolfe Attorney-Ronald J. Kransdorf Drive, Norwalk, Conn. 16850 22 Filed: July 31, 1972 57 ABSTRACT A tamper-proof key-operated lock is provided. The

21 Appl. No.1 276,741

check point for the lock is displaced from the locked position, and the lock tumblers, while biased when the lock is in the locked position, are not biased at the m the locked position to the check point to prevent spurious movement of the tumblers. A one bi check point. For preferred embodiments, a holdin force is applied to the tumblers as they are moved fro -piece, stationary asing spring is also provided to reduce the cost of the E 5 fis 1u S 00 T NW N a 2 RMM4 W 4 0 d b7 6A 5. .H 5% m4 CS m E "N e n "0 CT n W7 A m rT bs mTm I "8 T I nu N 1 m U C WH.

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12 Claims, 9 Drawing Figures PATENTED JUN 1 9 73 sum 1 or 2 PAIENIEU 3.739.611

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TAMPER RESISTANT LOCK BACKGROUND OF THE INVENTION Existing key-operated locks are normally of the sheer-pin type or of the tumbler type. Each type has a rotor or inner cylinder mounted for rotation in the bore of a stator or outer cylinder. With the sheer-pin type, a portion of each pin is in both the stator and the rotor with a spring for each pin in the stator biasing the stator pin down into the rotor to hold the cylinder against rotation. A proper key will raise each of the pins to a point where the break in the pin is at the junction be tween the inner and outer cylinders permitting the cylinders to rotate relative toeachother. With a tumbler type lock, each tumbler is mounted for lateral move ment in the inner cylinder, each tumbler being biased by its own spring to project from the bottom of the inner cylinder into a groove in the outer cylinder locking the cylinders together. A proper key inserted into the lock raises each tumbler against the action of its spring to a lateral position where it is fully within the inner cylinder, permitting the cylinders to rotate relative to each other.

Either of the locks described above may be tampered with by inserting asuitable tool into the lock and raising each tumbler or pin against the action of the spring, jiggling the inner cylinder as this is done until the turn bler or pin is felt to release. The spring helps to maintain the pin or tumbler in the desired position once it is found.

From the above it is apparent thatseveral features of existing locks contribute to the ease with which they may be picked or tampered with. First, and most important, the check point for the lock corresponds with the point at which the key is inserted. The tumblers or pins of the lock must thus be under spring pressure at this point. Without spring pressure at the check point, tampering would be virtually impossible since the person doing the tampering could move the tumbler or pin in only the upward direction. This means that the individual doing the picking would have to move the tumblers or pins up at a painfully slow pace in order to hit the precise required position at the right point in his jiggling of the lock. If he should overshoot the proper position on a single tumbler or pin, he would be required to return the inner cylinder to a position where the tumbler or pin is spring-biased and start the entire tampering operation again. Thus, while it might still be possible to tamper with a lock which is not spring-biased at the check point, the time required to tamper with such a lock, particularly if the lock had a fairly large number of tumblers or pins, would normally be prohibitive. Another deficiency with existing locks which aids in tampering is that, particularly with the sheer-pin lock, there is a certain tolerance inherent in the design. Lower tolerances reduces the amount of jiggling possible with the inner cylinder, making tampering far more difficult.

Aside from the problem of tampering, existing locks are also relatively complicated to assemble, requiring the placement of a separate spring, generally a coil spring, for each tumbler or pin. The cumulitive cost of the individual springs also adds to the cost of materials for the lock. Thus, the cost of both materials and assembly could be significantly reduced if a single spring could be utilized to bias the tumblers of a lock in place of the multiple springs now utilized.

SUMMARY OF THE INVENTION In accordance with the above, this invention provides a lock of the type having an inner cylinder mounted for rotation in an outer cylinder between a locked and an unlocked position, with at least two tumblers being sup ported for lateral movement in the inner cylinder. There is a means operative when the inner cylinder is in the locked position for biasing each of tumblers to a lateral position where they project from the inner cylinder, the tumblers moving away from the influence of the biasing means as the inner cylinder moves from the locked position toward the unlocked position. For a preferred embodiment of the invention, the biasing means is a single comb-shaped spring with a tine for each tumbler. The tines are bent to bear against the tumblers only when the lock is in the locked position. The lock also includes a means forming part of each tumbler for coacting with a proper key inserted in the lock to move each tumbler against the action of the bi asing means to a lateralposition in which it does not project from the inner cylinder. There is a means operative as the inner cylinder is moved by the key from the lockedto the unlocked position for holding each tumbler in its existing lateral position. For a preferred embodiment of the invention, this holding means is a permanent magnet mounted in the inner cylinder. Finally, the lock has a means operative when the inner cylinder has been rotated to a position where the tumblers are no longer influenced by the biasing means for testing to determine if any of the tumblers is projecting from the inner cylinder and for preventing the inner cylinder from being rotated to the un-locked position if any tumbler is found projecting.

The foregoing and other objects, features, and advantages of the invention will beapparent from the following more particular description of preferred embodiments of the invention as illustrated in the accompanying drawings.

BRIEF DESCRIPTION OF THE DRAWINGS FIG. 1 is a partially exploded, perspective view of a lock of a preferred embodiment of the invention.

FIG. 2 is a side sectional view of the lock shown in FIG. 1 showing the lock in the locked position with a key in the lock.

FIG. 3 is a sectional view along the line 3 3 of FIG. 2. I

FIG. 4 is a sectional view along the line 4-4 of FIG. 2 showing the lock in its locked position with no key in the lock.

FIG. 5 is a sectional view along the line 4-4 of FIG. 2 showing a slightly modified form of the look at its check point with the proper key inserted.

FIG. 6 is a sectional view along the line 4-4 of FIG. 2 showing the lock in its unlocked condition.

FIG. 7 is the same 'view as FIG. 5 with no key or the wrong key in the lock.

FIG. 8 is a sectional view along the line 4--4 of FIG. 2 for an alternative embodiment of the invention show ing the lock with the key in and in the locked position.

FIG. 9 is the same view as FIG. 81 for a second alternative embodiment of the invention.

DETAILED DESCRIPTION Referring now to FIGS. 1 through 4, it is seen that the lock of a preferred embodiment of the invention consists of an outer cylinder or stator 10 having a cylindrical bore 12. Outer cylinder 10 is preferably formed of a metal or other hard materal. An insert 14 is positioned in bore 12 and secured therein either by frictional engagement, welding, set screws or other suitable means. Insert 14 has a bore 16 extending at least partway along its length. A pair of slots 18 are formed in the walls of insert 14 on opposite sides thereof. Each slot 18 extends for slightly less than 90 around the cir-- cumference of the insert. The length of each slot 18 is determined by the number of tumblers.

An inner cylinder or rotor 20 is mounted for rotation in bore 16 of insert 14. Rotor 20 has a plurality of tumblers 22 supported for lateral movement therein. For purposes of illustration, five tumblers 22 have been shown in FIGS. 1 and 2. Each tumler 22 is in the shape of in inverted U with inner base surface 24 being of variable depth and adapted to coact with an inserted key 26 to raise the tumbler to a position shown in FIG. where it is fully within cylinder 20. For a preferred embodiment of the invention, spacers 28 are provided between each of the tumblers. However, tumbler receiving slots may be cut through a solid inner cylinder 20 eliminating the need for spacers 28.

A magnet 30 having a semi-circular cross section is mounted in inner cylinder 20 adjacent to tumblers 22. Magnet 30 extends along the length of inner cylinder 20 for a distance at least equal to the portion of the inner cylinder in which tumblers are mounted. As will be described in more detail later, magnet 30 functions to hold a tumbler 22 in its existing lateral position. For preferred embodiments of the invention, magnet 30 is a flexible plastic magnet which is cut to the desired length from a continuous strip. This arrangement is preferred since it is less expensive than other possible configurations.

A comb-shaped spring 32 is mounted in the upper of the slots 18 and is supported at one end between outer cylinder and insert 14. Spring 32 has a tine 33 for each tumbler 22 which tine is bent to bear against the corresponding tumbler, biasing it in a downward direction when the inner cylinder is in the locked position shown in FIG. 4. However, as may be best seen in FIG. 5, rotation of the inner cylinder out of the locked position, removes tumblers 22 from the influence of biasing spring 32. Being mounted in stator 10, spring 32 is also stationary.

The lock also has a bolt 34 with a cam track 36 formed in it. A pin 38 on the end of inner cylinder rides in cam track 36 and is adapted to lower the bolt when the inner cylinder has been rotated to the unlocked position shown in FIG. 6. Conversely, cam track 36 and pin 38 coact and operate in conjunction with spring 39 to raise bolt 34 when inner cylinder 20 is returned to the locked position shown in FIG. 4. As may be best seen in FIG. 1, a pin 41 formed on or attached to inner cylinder 20 rides in a 90 slot 43 formed in insert 14 to limit the relative rotation between the inner and outer cylinder.

OPERATION The lock of this invention is initially positioned as shown in FIG. 4 with bolt 34 up and inner cylinder 20 in the locked position, tumblers 22 being vertical. When the tumblers are in this position, spring 32 is operative to bias each of the tumblers to its lower-most lateral position. It is noted that the biasing force by spring 32 is greater than the holding force exerted by magnet 30 so that all of the tumblers are in fact in their lower-most position at this time regardless of their position at the time the tumblers come under the camming influence of the biasing spring.

When a key 26 is inserted in the lock, the teeth of the key coact with surfaces 24 on each of the tumblers to raise the tumbler to a selected position. If the proper key is inserted, each of the tumblers will be raised to a position where it is wholely within inner cylinder 20 (FIGS. 5 and 6). When the inner cylinder is rotated clockwise by the key, the tumblers are no longer under the influence of spring 32. However, they are retained in the position to which they are raised by the key by the holding action of magnet 30. It is noted that gravity will, for the most part, hold the tumblers against key 26. However, centrifical force caused by the rotation of the inner cylinder and/or vibration might cause the tumblers to be displaced slightly and magnet 30 is therefore required. However, the magnet is required to exert only a slight holding force. With the tumblers wholely within inner cylinder 20 as shown in FIG. 5 (ie. with a proper key inserted), the inner cylinder is able to pass the check point (shoulders 40 and 42) and be rotated to the unlocked position shown in FIG. 6. From FIG. 7 it is seen that with no key (dotted line) or the wrong key (solid line) a portion of at least one of the tumblers projects from inner cylinder 20 and engages either shoulder 40 at the right side of the upper of the slots 18 or shoulder 42 at the left side of the lower of the slots 18. This engagement at the check point prevents the inner cylinder from being rotated to the unlocked position.

FIG. 5 also illustrates a slight modification in the construction of the lock. From this figure it is seen that instead of having an outer cylinder 10 with a slotted insert 14 mounted therein, a thicker outer cylinder 10 is provided with grooves 18. The dimensions of the grooves 18 correspond to the dimensions of the slots 18. A recess is provided by the upper of the slots 18 for receiving spring 32.

FIG. 8 illustrates another alternative embodiment of the invention. For this embodiment of the invention, a magnet 50 mounted in stator 10 has been substituted for spring 32 to bias tumblers 22 in a downward direction when the inner cylinder is in its locked position. As with the spring 32, as the inner cylinder is rotated clockwise, the tumblers move away from the influence of magnet 50. Another modification with the embodiment of the invention shown in FIG. 8 is the use of a shoe 52 for each tumbler 22 which shoe is biased against the corresponding tumbler by a spring 54 to apply the holding force to the tumbler. As with the em: bodiments of the invention, shown in FIGS. 1-7, the biasing force by magnet 50 is greater than the holding force exerted by shoe 52 and spring 54. If desired, shoe 52 may be dispensed with and spring 54 bear directly against the tumbler. It should at this point he noted that while two modifications have been shown in FIG. 8, these modifications could be utilized separately in practicing the invention. Thus, a biasing magnet 50 could be utilized with a holding magnet 30 and a biasing spring 32 could be utilized with a holding spring 54.

The latter of these configurations has the advantage of permitting tumblers of non-magnetic material to be utilized.

It is noted that magnet 30 and shoe 52 are positioned in inner cylinder 20 to hold the tumblers against the left or training side of the slot in which the tumblers are supported. There is thus no play or movement with an improperly positioned tumbler (see FIG. 7) when it reaches the check point. This improves the tolerances of the lock and provides further protection against tampering.

The alternative embodiment of the invention shown in FIG. 9 differs from that shown in, for example, FIG. 4, in that holding magnet 30 has been eliminated. Since only a slight holding force sufficient to prevent movement as the result of vibration and centrifigal force is required, this holding force may be obtained with the embodiment shown in FIG. 9 in one of at least four ways. First, tumblers 22 may each be magnitized and the lock be adapted for use with a key of a ferrous material. Conversely the key used with the lock may be magnetized and the tumblers constructed of a ferrous material. With either of these arrangements, the magnetic attraction between the key and the tumbler provides the required holding force. These embodiments are, however, less desirable than those previously discussed in that limitations are placed on the type of key which may be utilized, and the use of magnetic tumblers would be more expensive than the use of a single plastic magnet 30. A third possible alternative is to replace at least one of the spacer 28 (FIG. 2) with a compression spring or similar element. This causes an axial force to be exerted on the tumblers and the remaining spacers, forcing adjacent tumblers and spacers into frictional engagement with each other to provide the required holding force. A fourth possible alternative is to magnitize the tumblers with adjacent surfaces of the tumblers being of opposite polarity. The resulting at-. traction of the tumblers causes frictional engagement which provides the required holding force.

A substantially tamper-proof lock has thus been provided, the tamperproof capability being obtained by displacing the check point position of the inner cylinder from the locked or key insertion position and by not biasing the tumblers when they are at the check point. For preferred embodiments, a tumbler holding means is provided to prevent movement of the tumblers once they leave the influence of the biasing means to assure that spurious movement of the tumblers does not occur as the inner cylinder is rotated from its locked position to the check point. A one-piece biasing spring is also provided significantly reducing the cost of assembling the lock.

While the invention has been particularly shown and described above with reference to preferred embodiments thereof, it will be apparent to one skilled in the art that the foregoing and other changes in form and detail may be made therein without departing from the spirit and scope of the invention.

What is claimed is:

l. A lock of the type having an inner cylinder mounted for rotation in an outer cylinder between a locked and an unlocked position, and at least two tumblers supported for lateral movement in the inner cylinder, comprising:

means operative when the inner cylinder is in said locked position for biasing each of said tumblers to a lateral position where they project from said inner cylinder; said tumblers moving away from the influence of said biasing means as the inner cylinder is moved from said locked position toward said unlocked position;

means forming part of each tumbler for coacting with a proper key inserted in the lock to move each tumbler against the action of said biasing means to a lateral position in which it does not project from said inner cylinder; and

means operative when said inner cylinder has been rotated to a position where the tumblers are no longer influenced by said biasing means for testing to determine if any of said tumblers is projecting from the inner cylinder and for preventing the inner cylinder from being rotated to the unlocked position if any tumbler is found projecting.

2. A lock as claimed in claim 1 including means oper ative as said inner cylinder is moved by the key from said locked to said unlocked position for holding each tumbler in its existing lateral position.

3. A lock as claimed in claim 2 wherein said tumbler holding means is a magnet mounted in said inner cylinder adjacent said tumblers, the tumblers being formed of a magnetic material.

4. A lock as claimed in claim 3 wherein said magnet is a flexible plastic magnet.

5. A lock as claimed in claim 2 wherein said tumbler holding means includes means for applying a frictional force to each of said tumblers.

6. A look as claimed in claim 5 wherein said means for applying a frictional force includes at least one spring mounted in said inner cylinder.

7. A lock as claimed in claim 1 wherein said inner cylinder is mounted in a bore in said outer cylinder, said bore having a pair of recesses on opposite sides thereof, at least in the area of the bore adjacent said tumblers, which extend from the position of an extending tumbler when the inner cylinder is in the unlocked position to the position of an extending tumbler when the inner cylinder is in the testing position.

8. A lock as claimed in claim 7 wherein each recess ends in a shoulder at the testing positions end thereof, said shoulder coacting with an extending tumbler to prevent the inner cylinder from being rotated to the unlocked position.

9. A lock as claimed in claim 7 wherein said outer cylinder includes a hollow cylinder having a slotted insert mounted therein, the slots in said insert forming said pair of recesses.

10. A lock as claimed in claim 1 wherein said biasing means is a magnet mounted in said outer cylinder in a position adjacent said tumblers when the inner cylinder is in the locked position.

11. A lock as claimed in claim 1 wherein said biasing means is a single comb-shaped spring mounted in said outer cylinder, said spring having a tine for each of said tumblers.

12. A lock as claimed in claim 11 wherein each of said tines is shaped to cam the corresponding tumbler to a position projecting from the bottom of inner cylinder as the inner cylinder is moved from the unlocked to the locked position and to bias the tumber to that position only when the inner cylinder is in the locked positron.

l l I k 

1. A lock of the type having an inner cylinder mounted for rotation in an outer cylinder between a locked and an unlocked position, and at least two tumblers supported for lateral movement in the inner cylinder, comprising: means operative when the inner cylinder is in said locked position for biasing each of said tumblers to a lateral position where they project from said inner cylinder; said tumblers moving away from the influence of said biasing means as the inner cylinder is moved from said locked position toward said unlocked position; means forming part of each tumbler for coacting with a proper key inserted in the lock to move each tumbler against the action of said biasing means to a lateral position in which it does not project from said inner cylinder; and means operative when said inner cylinder has been rotated to a position where the tumblers are no longer influenced by said biasing means for testing to determine if any of said tumblers is projecting from the inner cylinder and for preventing the inner cylinder from being rotated to the unlocked position if any tumbler is found projecting.
 2. A lock as claimed in claim 1 including means operative as said inner cylinder is moved by the key from said locked to said unlocked position for holding each tumbler in its existing lateral position.
 3. A lock as claimed in claim 2 wherein said tumbler holding means is a magnet mounted in said inner cylinder adjacent said tumblers, the tumblers being formed of a magnetic material.
 4. A lock as claimed in claim 3 wherein said magnet is a flexible plastic magnet.
 5. A lock as claimed in claim 2 wherein said tumbler holding means includes means for applying a frictional force to each of said tumblers.
 6. A lock as claimed in claim 5 wherein said means for applying a frictional force includes at least one spring mounted in said inner cylinder.
 7. A lock as claimed in claim 1 wherein said inner cylinder is mounted in a bore in said outer cylinder, said bore having a pair of recesses on opposite sides thereof, at least in the area of the bore adjacent said tumblers, which extend from the position of an extending tumbler when the inner cylinder is in the unlocked position to the position of an extending tumbler when the inner cylinder is in the testing position.
 8. A lock as claimed in claim 7 wherein each recess ends in a shoulder at the testing positions end thereof, said shoulder coacting with an extending tumbler to prevent the inner cylinder from being rotated to the unlocked position.
 9. A lock as claimed in claim 7 wherein said outer cylinder includes a hollow cylinder having a slotted insert mounted therein, the slots in said insert forming said pair of recesses.
 10. A lock as claimed in claim 1 wherein said biasing means is a magnet mounted in said outer cylinder in a position adjacent said tumblers when the inner cylinder is in the locked position.
 11. A lock as claimed in claim 1 wherein said biasing means is a single comb-shaped spring mounted in said outer cylinder, said spring having a tine for each of said tumblers.
 12. A lock as claimed in claim 11 wherein each of said tines is shaped to cam the corresponding tumbler to a position projecting from the bottom of inner cylinder as the inner cylinder is moved from the unlocked to the locked position and to bias the tumber to that position only when the inner cylinder is in the locked position. 